1. Field of the Invention
The present invention relates to a novel organometallic compound, and more particularly, to a light-emitting organometallic compound with improved light-emitting property, in which a germanium substituent is introduced, inhibiting intermolecular interaction, an organic electronic device, or an organic light-emitting diode using the organometallic compound.
2. Description of the Related Art
Organic light-emitting diode (OLED) is a kind of organic electronic device, which basically includes an organic thin film including an organic light-emitting layer is sandwiched between two electrodes, in which at least one of the electrodes is transparent, to utilize the light in visible-light range emitted from the organic light-emitting layer upon application of a proper voltage, e.g., direct current of 5˜10V, for example.
The organic light-emitting diode is very thin, with actual thickness including the electrodes ranging only several micrometers or less, and is a self-light emitting diode that emits light directly from the diode itself, and accordingly has various advantages because it has a fast responsivity, provides a display device with a broad viewing angle, requires simple manufacturing process, achieves flexibility using organic thin film, can be fabricated by not only vacuum process, but also printing process in a solution state as need arises. Thus, the organic light-emitting diode is gaining a huge attention as a next-generation display and illumination, for which active researches are under way.
Generally, the organic light-emitting layer includes at least one of organic and organometallic compound or organic/inorganic hybrid materials, and is divided into two types according to light-emitting mechanism: one is a fluorescence type based on quenching of singlet exciton, and the other is a phosphorescence type using quenching of triplet exciton.
The phosphorescence type using the triplet exciton, in particular, has been applied to organic light-emitting diodes relatively recently compared to the fluorescence one (refer to U.S. Pat. No. 6,303,238.). Since the latter type creates a higher efficiency than the fluorescence one, research on related technologies has been conducted very briskly.
For the organic light-emitting diode of the phosphorescence type, the most important key element is phosphorescent light-emitting substance such as widely known organometallic compounds. Among these, the organometallic compounds based mainly on iridium prevail.
The iridium organometallic compounds have an advantage in that the optical and electrical properties of the final iridium organometallic compounds are adjustable by regulating the chemical structure of a ligand coordinate bond to an iridium atom, to enable synthesis of organometallic compounds that suit various requirements.
Specifically, the iridium organometallic compounds having phenylpyridine as a basic structure of ligand, e.g. tris(2-phenylpyridine)iridium (III) (hereinafter referred to as ‘Ir(ppy)3’), are the most widely known (refer to JP 3992929.).
However, the conventionally known iridium organometallic compound such as Ir(ppy)3 has limited efficiency due to triplet annihilation caused by intermolecular interaction when used as a light-emitting layer of an organic light-emitting diode. Also, the solubility in a solvent may not be sufficient when used in the solution process, instead of vacuum deposition.
Therefore, there are growing requests to develop light-emitting organometallic compounds that are applicable to the solution process and have an improved light-emitting property.
Accordingly, the inventors of the present invention have completed the present invention, in the course of researching solution to the foregoing shortcomings, after synthesizing a novel organometallic compound with improved emission efficiency due to inhibited intermolecular interaction by the introduction of a germanium substituent into an iridium ligand and confirming that the light-emitting property of the compound is improved compared to that of conventional organometallic compounds, and thus is applicable to an organic light-emitting diode.